Problem: $ { \left[\begin{array}{rr}{-2} & {2} \\ {3} & {-1} \\ {-1} & {1}\end{array}\right]+\left[\begin{array}{rr}{-1} & {-2} \\ {4} & {-1} \\ {3} & {2}\end{array}\right] = {?} } $
Explanation: To find the sum of two matrices, add the corresponding items between each matrix. ${\left[\begin{array}{rr}{-2}+{-1} & {2}+{-2} \\ {3}+{4} & {-1}+{-1} \\ {-1}+{3} & {1}+{2}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{rr}{-3} & {0} \\ {7} & {-2} \\ {2} & {3}\end{array}\right]}$